1. Field of the Invention
The present invention is in the field of dielectric coupling of starter electrodes for traverse electrical excitation of gas laser cavities.
2. Description of the Prior Art
Conventional pulsed transversely excited atmospheric pressure (TEA) gas lasers use metal electrodes which are profiled to provide a uniform electric field for excitation of the gas lasing medium. This results in excitation of a substantially larger volume of gas between the metal electrodes than the limited amount of gas from which optical laser energy is extracted; i.e. from the optical mode volume. When conducting electrodes are used, the only way that a uniform glow discharge, free of arcing and high current streamers, can be obtained is to shape the electrodes such that there are wider gaps at the edges than in the center of the discharge, thus the prior use of convex shaped electrodes. However, a problem exists in that optical energy is extracted only from a small volume with circular cross section centered between the electrodes.
One way to substantially increase the efficiency of pulsed gas lasers is to obtain a closer match between the volume of excited gas and the mode volume of the optical cavity. Previous approaches have been tried with this objective in mind, but have exhibited operational deficiencies. One approach used is coaxial electrode geometry. This type device does not however give a good TEM.sub.oo spatial mode output, requires drilling of end mirrors for mounting of the central electrode, and results in a strong radial dependence of volumetric energy deposition.